Table 3.

Common challenge topics found in the studies.

Topic		Directa	Indirectb	Total
Behavior change		8	10	18
	Barriers to change	5	4	9
Interaction		23	20	43
	Engagement	12	2	14
	Trust	5	7	12
	Burden of use	5	4	9
	Learning	1	7	8
Technical feasibility		13	7	20
	Source datac	8	3	11
	Performance	5	4	9

^aThe authors of the publication recorded the topic as a challenge to the implementation of the app.

^bThe authors addressed the topic but not directly as a challenge to the implementation of the app.

^cThe data that underlie the information that is viewed on the app. This is typically a database of product information.